Her employer denies the
woman's firing was tied to her ongoing complaints about safety concerns, but as
Carter Evans reported on "CBS This Morning," she believes it sends an
ominous message.

Asked if she feels like
she's a target, Donna Busche said: "Absolutely."

Until Tuesday, Busche was
the manager of Environmental and Nuclear Safety at the Hanford Nuclear
Reservation. CBS News interviewed her in October after one of her colleagues was also fired. They had raised concerns about the $13 billion cleanup of a treatment
facility in southeastern Washington State.

There are currently 53
million gallons of nuclear waste held in 177 underground tanks. Many have leaked radioactive material into the ground.

In October, Busche said,
"We raised technical issues and have received harassment, retaliation. The fact that he was terminated, it sent a resounding message to me, right?
And heightened my sense of awareness that I was probably next."

She was next. Late Tuesday, her
employer, a Hanford cleanup subcontractor, issued this statement: "Though
URS supports Ms. Busche's right to raise concerns and to express her personal
views, we do not agree with her assertions that she suffered retaliation or was
otherwise treated unfairly. Ms. Busche's employment was terminated...due to
issues unrelated to her purported concerns."

CBS News spoke with Busche via
Skype. She said, "URS
gave me no reason for my termination other than 'unprofessional conduct.' They
gave me no documentation. They gave me no explanation."

Her colleague, fellow
safety official Walter Tamosaitis, was fired in October. Both he and Busche
have been outspoken about dangers at the plant. Among their biggest concerns is
a design flaw they claim could lead to a deadly hydrogen explosion or
worse -- a nuclear chain reaction.

Busche says their firings
will have a chilling effect on anyone else who raises safety concerns at Hanford. She said via Skype, "One of my previous subordinates says
that they're actually afraid of getting fired for doing their job."